II.] STRUCTURE OF BLOOD. 43 



stem, it then contains 995 c. m. ; empty it into 

 the measuring glass. Fill the small pipette 

 with freshly drawn blood up to the line marked 

 5 c. m. ; empty it into the measuring glass, and 

 with the fluid in the measuring glass wash out 

 the blood sticking to the inside of the tube ; 

 thoroughly mix the blood and salt solution with 

 the glass spatula, place a small drop of the 

 mixture in the centre of the glass cell and 

 over it lay a cover-slip, arrange the springs on 

 the cover-slip to keep it in position, and under 

 a high power count the number of red corpuscles 

 in ten of the squares which are marked at the 

 bottom of the glass cell. 



Since the depth of the cell is J mm. and the 

 side of each square is T ^ mm., there is beneath 

 each square ^y c. m. of the mixture, i.e. -nnjWff 

 c. m. of blood, hence the number of corpuscles 

 in 10 squares multiplied by 10,000 gives the 

 number of corpuscles in 1 c. m. blood. 



DEMONSTRATIONS. 



The method of using the simple and Strieker's 

 warm stage. 



The 'platelets' of frog's or newt's blood (cf. 

 p. 387). 



Specimens to show the chief stages of indirect 

 nuclear division (cf. p. 395). 



NOTE. If the brain of a frog be destroyed, a drop of cnrari injected 

 under the skin, and the frog be left for a day in about inch of water, 

 the lymph sacs will become tilled with lymph containing numerous 

 white corpuscles, many in a state of active amoeboid movement 



